Blur correction apparatus

ABSTRACT

A blur correction apparatus is provided that includes a blur correction mechanism, a locking member, a shift drive processor and an unlocking driver. The blur correction mechanism compensates for camera shake by driving a movable portion provided with one of a correction lens and an imaging device. The locking member restricts movement of the movable portion within a locked range of motion. The shift drive processor moves the movable portion a predetermined distance toward a center of the locked range of motion when locking by the locking member is released and the predetermined distance is shorter than the distance from the movable portion to the center. The unlocking driver moves the locking member to an unlocked position after moving the movable portion the predetermined distance away from the locking member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical blur correction apparatuswhich prevents the occurrence of image blur by moving a lens or an imagesensor in accordance with the deviation of an optical axis caused bycamera shake.

2. Description of the Related Art

Lens shift is known as one type of optical blur correction mechanism. Inthe lens shift type, a gyroscopic sensor and a correction lens arearranged in a lens barrel and image blur due to camera shake is canceledby driving the correction lens based on an output of the gyroscopicsensor. A movable portion on which the correction lens is mounted isloosely supported by a lens barrel body, for example by an elastic body,and the position of the movable portion is controlled within a specificrange (range of motion) in a plane perpendicular to an optical axis byan electromagnetic actuator including a coil, a magnet, a yoke, and thelike. The movable portion can move substantially freely within the rangeof motion. Therefore, due to gravity, the movable portion drops downwardwithin the range of motion when blur correction control is in an OFFstate and the center of the correction lens deviates from the opticalaxis.

Accordingly, a mechanical locking mechanism may be used to fix themovable portion in place by fitting a lock pin (locking member) into alock hole formed in the movable portion. Namely, when the blurcorrection control is in an OFF state, the center of the correction lensis fixed on the optical axis by the locking mechanism. However, sincethere is play in such a mechanical locking mechanism, the correctionlens can still deviate in the direction of gravity within the range ofplay when the blur correction control is suspended in a locked state.Accordingly, unintentional blur can occur instantaneously in a finderimage or monitor image even in the locked state. To solve such aproblem, US 2004/0017485 A1 discloses a system that detects thedirection of gravity when the movable portion is locked and thecorrection lens is moved beforehand to the deviation position before theblur correction control is turned off.

SUMMARY OF THE INVENTION

Meanwhile, when a locking member is in contact with a movable portion,friction may obstruct a movement of the locking member toward anunlocked position during a release operation of the mechanical lock.

Therefore, one aspect of the present invention is to provide a blurcorrection system provided with a mechanical locking mechanism that caneasily and rapidly release locking.

According to the present invention, a blur correction apparatus isprovided that includes a blur correction mechanism, a locking member, ashift drive processor and an unlocking driver.

The blur correction mechanism compensates for camera shake by driving amovable portion provided with one of a correction lens and an imagingdevice. The locking member restricts movement of the movable portionwithin a locked range of motion. The shift drive processor moves themovable portion a predetermined distance toward a center of the lockedrange of motion when locking by the locking member is released and thepredetermined distance is shorter than the distance from the movableportion to the center. The unlocking driver moves the locking member toan unlocked position after moving the movable portion the predetermineddistance away from the locking member.

For example, the predetermined distance is equal to or less than 50% ofthe distance the movable portion is moved to the center. Morepreferably, the predetermined distance is equal to or less than 20%thereof. The movable portion is moved by the shift drive processor whenblur correction starts.

Further, for example, the movable portion includes a circular frameportion and the locking member is a lock ring which surrounds theperiphery of the circular frame portion. A plurality of protrusions isarranged on an outer circumference of the circular frame portion and aplurality of recesses corresponding to the plurality of protrusions isarranged on an inner circumference of the circular lock ring. The lockring is movable between a locked position and unlocked position. In thelocked position, movement of the movable portion is restricted bycontact between the protrusions and the inner circumference of thecircular lock ring. In the unlocked position, the protrusions arepositioned in their respective recesses so that the movable portion ismade movable for blur correction.

Further, it is preferable that the movable portion is suspended in acurrent position by the blur correction mechanism when a releaseoperation is performed in a state in which the movable portion is lockedby the locking member.

Further, the present invention provides a lens barrel that includes theblur correction mechanism, the locking member, the shift drive processorand the unlocking driver.

The blur correction mechanism compensates for camera shake by driving amovable portion provided with the correction lens. The locking memberrestricts movement of the movable portion within the locked range ofmotion. The shift drive processor moves the movable portion thepredetermined distance toward the center of the locked range of motionwhen locking with the locking member is released. The predetermineddistance is less than the distance from the movable portion to thecenter. The unlocking driver moves the locking member to the unlockedposition after moving the movable portion by the predetermined distanceaway from the locking member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating a structure of acamera of the present embodiment.

FIGS. 2A-2C include a perspective front view of a blur correctionmechanism of the present embodiment, a front view in an unlocked state,and a front view in a locked state.

FIGS. 3A and 3B include views schematically illustrating the range ofmotion of a correction lens in an unlocked state and a locked state.

FIG. 4 is a perspective view schematically illustrating a relationbetween movement of a camera due to camera shake and the camera's X andY axes of orientation.

FIG. 5 is a front view illustrating a relation among a camera body, thecorrection lens, and the X and Y axes.

FIG. 6 is a block diagram of a blur correction control to be performedby a lens CPU.

FIG. 7 is a flowchart of a main program to be performed by a camera CPU.

FIG. 8 is a flowchart of a main program to be performed by the lens CPU.

FIG. 9 is a flowchart of a lock initialization operation to be performedby the lens CPU.

FIG. 10 is a flowchart of a timer interruption process with a cycle of 1ms to be performed by the lens CPU in the first embodiment.

FIG. 11 is a flowchart of a centering drive process to be performed bythe lens CPU.

FIG. 12 is a flowchart of a shift drive process to be performed by thelens CPU.

FIGS. 13A-13D include schematic views illustrating four states in whichthe correction lens is deviated by gravity within a locked range ofmotion.

FIG. 14 is a flowchart of a current position maintenance drive processto be performed by the lens CPU.

FIG. 15 is a flowchart of a blur correction drive process.

FIG. 16 is a flowchart of a timer interruption process with a cycle of 1ms to be performed by the lens CPU in the second embodiment.

FIG. 17 is a graph indicating positional movement of the correction lensand timing of unlocking in a sinusoidal-drive unlocking process (gradualunlocking process) of the second embodiment.

FIG. 18 is a flowchart of the sinusoidal-drive unlocking process(gradual unlocking process).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be describedwith reference to the drawings. FIG. 1 is a block diagram illustrating astructure of a camera on which a blur correction mechanism of a firstembodiment of the present invention is mounted. In the drawing, onlystructures related to the present invention are schematicallyillustrated.

In the present embodiment, a camera 10 may be a digital single-lensreflex camera in which a lens barrel 12 is detachably attachable to acamera body 11. Further, in the present embodiment, a blur correctionmechanism 13 is arranged in the lens barrel 12. That is, the blurcorrection mechanism 13 having a correction lens 14 for blur correctionis configured between two imaging lenses 15A, 15B. Incident light fromthe imaging lens 15A, which passes along an optical axis L via thecorrection lens 14 and the imaging lens 15B, forms an image on animaging device 16 in the camera body 11.

A camera CPU 17 and a lens CPU 18 are arranged in the camera body 11 andthe lens barrel 12, respectively. The camera CPU 17 is connected to amain switch 19, a photometric switch 20, and a release switch 21.Further, the camera CPU 17 is connected to the lens CPU 18 through aplurality of electrodes of a lens mount (not illustrated) along with apower line and ground line. Here, the camera CPU 17 is connected to avariety of other devices for performing a variety of controls for theentire camera.

A blur correction switch 22 to turn a blur correction control ON/OFF isarranged in the lens barrel 12 and is connected to the lens CPU 18.Further, angular velocity sensors 23X and 23Y, which detect angularvelocities about the Y and X axes, respectively, which are the verticalaxis and horizontal axis of a camera and are perpendicular to theoptical axis L, are arranged in the lens barrel 12. Signals detected bythe angular velocity sensors 23X, 23Y are input to the lens CPU 18. Whenthe blur correction control is ON, the lens CPU 18 calculates targetpositions where to move the correction lens 14 along the X and Y axes tocompensate for camera shake based on angular velocities detected aboutthe respective axes by the angular velocity sensors 23X and 23Y, andlens information 38 such as a focal length f.

The correction lens 14 is driven by electromagnetic interaction betweena coil (not illustrated) arranged on a movable portion 28 that holds thecorrection lens 14, and a yoke arranged on a fixed portion that is fixedto the lens barrel 12, for example. Current supplied to the coil iscontrolled by an X-direction drive controller 24X and a Y-directiondrive controller 24Y. Position sensors 25X, 25Y using Hall elements orthe like, for example, are arranged at the movable portion 28 whichholds the correction lens 14, so that a position of the correction lens14 is detected for feedback to the lens CPU 18. That is, the lens CPU 18calculates an amount of current supplied to the coil from the targetpositions of the correction lens 14 that are calculated based on thesignals of the angular velocity sensors 23X, 23Y and the currentpositions of the correction lens 14 obtained from the position sensors25X, 25Y. The CPU 18 then outputs the amounts of current to theX-direction drive controller 24X and the Y-direction drive controller24Y.

The blur correction mechanism 13 is provided with a mechanical lockingmechanism 26 and a lock detection sensor 26S to detect locking status.The locking mechanism 26 is for maintaining the center of the correctionlens 14 on the optical axis L and is controlled by a lock ringcontroller 27 based on instructions from the lens CPU 18. The currentlocking status is indicated to the lens CPU 18 by the lock detectionsensor 26S.

Here, a communication port of the lens CPU 18 and a communication portof the camera CPU 17 are connected through the electrodes of the lensmount, as described above. Data communication is performed therebetween, as described later.

FIGS. 2A to 2C are external views of the blur correction mechanism 13 ofthe present embodiment. FIG. 2A is a perspective front view. FIG. 2B isa front view in an unlocked state and FIG. 2C is a front view in alocked state.

As illustrated in the drawings, the correction lens 14 is held by themovable portion 28, which has a circular frame, approximately at itscenter. For example, four protrusions 28P protruding outward in theradial direction are arranged on an outer circumference of the circularframe of the movable portion 28 approximately at equally spacedintervals along the outer circumference. A circular lock ring 30 isarranged at the periphery of the circular frame of the movable portion28 to surround the circular frame. A circular clearance 29 is formedbetween the lock ring 30 and the circular frame.

The inner diameter of the lock ring 30 is arranged to have a dimensionso that the respective protrusions 28P of the movable portion 28 makecontact with the inner circumference of the lock ring 30 disregardingtolerance. Recesses 30P corresponding to the number of protrusions 28Pare formed at the inner circumference lock ring 30, approximately atequally spaced intervals along the inner circumference. As describedlater, the recesses 30P in cooperation with the protrusions 28P definethe range of motion of the correction lens 14 for blur correction.

The lock ring 30 is contained in a casing (fixed portion) 31 that has anapproximately cylindrical external appearance and is rotatable about theoptical axis L in the casing 31. Rotation of the lock ring 30 isperformed by a rack-and-pinion mechanism which is arranged at the outercircumference of the lock ring 30, for example. That is, a rack 30R isarranged on the outer circumference of the lock ring 30 and is engagedwith a pinion 32 that is arranged on the casing 31 side. The pinion 32is driven by a stepping motor (not illustrated) which is fixed in thecasing 31.

Cutouts 30A, 30B for detecting locking status from a rotational positionof the lock ring 30 are arranged on the outer circumference of the lockring 30. A photo-interrupter (lock detection sensor) 26S that is used incooperation with the cutouts 30A, 30B is arranged in the casing 31. Thatis, light is detected by the photo-interrupter 26S through the cutout30A in the unlocked state as illustrated in FIG. 2B, whereas light isdetected through the cutout 30B in the locked state as illustrated inFIG. 2C.

Further, the movable portion 28 includes a plurality of flat plateportions 28A which extend from the circular frame outward in the radialdirection, so that the coil for driving the movable portion 28 and thelike are mounted thereon. In the casing 31, the front side and the backside of the flat plate portions 28A are supported by bearings (notillustrated), so that movement in the optical axis direction isrestricted.

Next, the range of motion of the correction lens 14 in the presentembodiment will be described with reference to FIGS. 2A to 2C, 3A, and3B. FIGS. 3A and 3B are views schematically illustrating the range ofmotion of the correction lens 14 in the unlocked state and the lockedstate, respectively.

In the unlocked state of FIG. 2B, the lock ring 30 is positioned so thatthe protrusions 28P of the movable portion 28 are aligned with therecesses 30P, respectively. In this state, movement of the movableportion 28 is restricted by contact of the protrusions 28P with the sidewalls of the recesses 30P. Here, the range of motion of the correctionlens 14 is denoted by a rectangular range (unlocked range of motion) 33shaded in FIG. 3A. On the other hand, in the locked state of FIG. 2C,the lock ring 30 is rotated clockwise from the position of FIG. 2B, sothat each protrusion 28P is in contact with an arc-shapedinner-circumferential surface of the lock ring 30. Accordingly, movementof the movable portion 28 upward, downward, rightward, or leftward isrestricted, so that the correction lens 14 is fixed with its centerbeing aligned with the optical axis L.

However, since tolerance exists between the protrusion 28P and thearc-shaped inner circumferential surface, the correction lens 14 ismovable, even in the locked state, in a shaded circular range (lockedrange of motion) 34 centered on the optical axis L as illustrated inFIG. 3B.

Next, a blur correction drive process of the present embodiment will bedescribed in detail with reference to FIGS. 4 to 6. FIG. 4 is aperspective view schematically illustrating the movement of the cameradue to camera shake with respect to the X and Y axes. FIG. 5 is a frontview illustrating the relationship between the camera body 11 and thecorrection lens 14 with respect to the X and Y axes.

As illustrated in FIG. 4, during photography with the camera, rotation(yaw) about the vertical axis (Y axis) causes image blur in thehorizontal direction (X-axis direction) and rotation (pitch) about thehorizontal axis causes image blur in the vertical direction (Y-axisdirection). Accordingly, shifting the correction lens 14 in the X-axisdirection by a proper amount—as determined by detected rotationalmovement about the Y axis—can compensate for image blur in the X-axisdirection. Likewise, shifting the correction lens 14 in the Y-axisdirection by a proper amount—as determined by detected rotationalmovement about the X axis—can compensate for image blur in the Y-axisdirection.

FIG. 6 is a block diagram of the blur correction control performed bythe lens CPU 18. The correction process is performed as an interruptionprocess, for example, at predetermined time intervals (e.g., 1 ms).

Analog angular velocity signals about the Y axis and the X axis obtainedby gyroscopes of the angular velocity sensors 23X, 23Y are input to A/Dports (A/D1, A/D2) of the lens CPU 18 and converted into digital signalsby the A/D calculation units 35X, 35Y. The angular velocities about theY axis and the X axis are integrated by angle calculation units 36X, 36Yto calculate rotational angles (a yaw angle θY and a pitch angle θX)about the Y axis and the X axis. The drive positions of the correctionlens 14 in the X direction and Y direction for compensating againstimage blur are calculated by lens drive position calculation units 37X,37Y based on the yaw angle, the pitch angle, and the lens information 38such as the focal length f stored in a memory.

When the signal from the blur correction switch 22 input through a port4 is ON, a controller 39 calculates the differences between the targetposition coordinates X, Y and the current position coordinates X, Y ofthe correction lens 14, where the target position of the correction lens14 is defined by the drive position coordinate X in the X-axis directionand the drive position coordinate Y in the Y-axis direction, which arecalculated by the lens drive position calculation unit 37X, 37Y.Automatic control processors 40X, 40Y perform processes such as a PIDprocess thereon. Outputs of the automatic control processors 40X, 40Yare supplied to the X-direction drive controller 24X and the Y-directiondrive controller 24Y through a port 1 and a port 2, respectively, tocontrol current supplied to an X-direction coil 41X and a Y-directioncoil 41Y arranged in the blur correction mechanism 13.

The position of the movable portion 28, that is, the current positioncoordinates of the correction lens 14 in the X-axis direction and theY-axis direction, are calculated by the X-direction drive controller 24Xand the Y-direction drive controller 24Y based on signals from the Hallsensors (position sensors) 25X, 25Y and input to the lens CPU 18 throughA/D ports (A/D3, A/D4) as signals of current position coordinates X, Y.The signals are converted into the digital signals of the currentposition coordinate X and the current position coordinate Y by A/Dcalculation units 43X, 43Y and feedback thereof is performed asdescribed above. Accordingly, when the blur correction switch 22 is ON,the target position of the correction lens 14, which corresponds to thedrive position coordinates, is calculated based on the outputs of theangular velocity sensors 23X, 23Y and the correction lens 14 is drivenin the X axis direction and the Y axis direction based on the abovetarget values.

Here, based on the ON/OFF state of the blur correction switch 22, thelens CPU 18 rotates the lock ring 30 by driving a locking motor 44 suchas a stepping motor, with the lock ring controller (driver) 27 connectedto a port 3. That is, the position the lock ring 30 is switched betweenan unlocked position (FIG. 2B) and a locked position (FIG. 2C). Thephoto-interrupter (lock detection sensor) 26S detects whether the lockring 30 is positioned in the unlocked position or the locked position.

Next, a main operation process performed by the camera CPU 17 and thelens CPU 18 will be described with reference to FIGS. 1, 6, 7, and 8.The processes of FIGS. 7 and 8 start when a main switch 19 on the camerabody 11 is turned on. Note that in the following descriptions, the lensbarrel 12 is attached to the camera body 11.

FIG. 7 is a flowchart for the camera CPU 17. In step S100, it isdetermined whether or not the release switch 21 is ON. When the releaseswitch 21 is ON, the process proceeds to step S120. When the releaseswitch 21 is not ON, communication between the camera CPU 17 the lensCPU 18 starts in step S102 and the lens CPU 18 is required to perform alocking initialization operation.

In step S104, it is determined whether or not the photometric switch 20is ON. This process is repeated until the photometric switch 20 isturned on. When it is determined that the photometric switch 20 is ON,the process proceeds to step S106 where the camera CPU 17 establishescommunication with the lens CPU 18 and informs the lens CPU 18 that thecamera CPU 17 will start through-the-lens image operation.

In steps S108 to S116, capture and display of the through-the-lens imageare carried out. That is, an AE process is performed in step S108 and anAF process is performed in step S110. In step S112, the imaging device(CCD) 16 accumulates charges based on a focus position set in step S110and the exposure determined in step S108. Then, in step S114, forexample, pixel signals accumulated in the imaging device (CCD) 16 may beread out and output as field images. In step S116, the output imagesignal is output to a monitor (not illustrated) and the through-the-lensimage is displayed.

Next, in step S118, it is determined whether or not the release switch21 is ON. When the release switch 21 is not ON, the process proceeds tostep S130. When the release switch 21 is ON, the process continues tostep S120 and the camera CPU 17 establishes communication with the lensCPU 18 and informs the lens CPU 18 that the camera CPU 17 will start arelease process. In steps S122 to S128, a still image is photographed.That is, in step S122 the imaging device (CCD) 16 carries out chargeaccumulation based on the focus position set in step S110 and theexposure determined in step S108. Then, in step S124, for example, thecharges accumulated in the imaging device (CCD) 16 for all of the pixels(a frame image) are read out. In step S126, the output image signal isstored in a non-volatile image memory (not illustrated). In step S128,the image is displayed on the monitor (not illustrated).

Next, in step S130, it is determined whether or not the photometricswitch 20 is ON. When it is determined that the photometric switch 20 isON, the process returns to step S106. When it is determined that thephotometric switch 20 is not ON, the process returns to step S102 andthe above processes are repeated until the main switch 19 of the camerabody 11 is turned off or the camera enters a sleep mode.

FIG. 8 is a flowchart for the lens CPU 18. In steps S200 and S202,initialization of a status register is performed. In step S200,initialization is performed on a flag SR which indicates the status ofthe blur correction control (blur correction status). In step S202,initialization is performed on an RLS flag which indicates the releasestatus. That is, both SR and RLS are set to zero. Three statuses areindicated by the SR flag. When “SR=0”, a locking process (initializationoperation) for the lock ring 30 has already been performed. When “SR=1”,the blur correction control is in an OFF state. When “SR=2”, the blurcorrection control is in an ON state. Further, two statuses areindicated by the RLS flag. When “RLS=0”, a through-the-lens image isdisplayed. When “RLS=1”, a release operation is underway.

After the initialization of the SR and RLS flags is completed, in stepS204, it is determined whether or not a communication request existsfrom the camera CPU 17. The determination is repeated until acommunication request is received from the camera CPU 17. When acommunication request from the camera CPU 17 is detected by the lens CPU18, it is determined whether the communication is requesting lockinginitialization (request for a locking operation by the lock ring 30),informing of execution of a through-the-lens image display by the camerabody 11, or informing of execution of a release operation in the camerabody 11, respectively in steps S206, S208, and S210.

In the case of a locking initialization request, the lockinginitialization operation indicated in FIG. 9 is performed in step S212.As illustrated in FIG. 9, the first part of the locking initializationoperation is a centering drive process that is carried out in step S300to align the correction lens 14 with the optical axis. As illustrated inthe flowchart of FIG. 11, in the centering drive process the position ofthe correction lens 14 is detected based on the output of the Hallsensors 25X, 25Y (see FIG. 6) in step S500. Then, in step S502, thedrive position (X, Y), which is the target position of the correctionlens 14, is assigned the coordinates (0,0) by the controller 39 so thatit corresponds to the optical axis and the center of the range of motion33, 34 (see FIG. 3). Next, in steps S504 and S506, an automatic controlcalculation is performed based on the current position and the targetposition, and the correction lens 14 is moved to the center position(0,0) by driving the image blur correction mechanism 13 based on thecalculation result.

Next, in step S302, the lock ring 30 is rotated to the locked positionby driving a locking motor 44. In step S304, power supplied to the coils41X, 41Y constituting an electromagnetic actuator is discontinued anddriving of the correction lens 14 is stopped. In step S306, the SR flagindicating a blur correction status is set to satisfy “SR=0” to indicatethat the locking initialization operation has been performed, and thenthe locking initialization operation is finished.

In a case that the communication from the camera CPU 17 is determined tobe a notification to display a through-the-lens image in step S208, theRLS flag indicating the release status is set to satisfy “RLS=0” in stepS214 to indicate that a through-the-lens image is being displayed. Whenthe communication from the camera CPU 17 is determined to be anotification to perform release operation in step S210, the RLS flagindicating the release status is set to satisfy “RLS=1” to indicate thata release operation is being performed. The processes in steps S204 toS210 are repeated while the lens CPU 18 is powered ON.

Further, the timer interruption process illustrated in the flowchart ofFIG. 10 occurs in the lens CPU 18 with a cycle of 1 ms. In thefollowing, a timer interruption process with a cycle of 1 ms will bedescribed with reference to FIGS. 2, 6, 10, and 11.

In step S400 of the timer interruption process with a cycle of 1 ms, itis first determined whether or not the RLS flag satisfies “RLS=1”, thatis, whether or not the current status is under a release operation. WhenRLS≠1, which indicates that a release operation is not in effect, theprocess proceeds to step S402 and the ON/OFF state of the blurcorrection switch 22 is detected to determine whether or not the blurcorrection switch 22 is in an ON state.

When the blur correction switch 22 is in an OFF state, the processproceeds to step S404 where it is determined whether the SR flagsatisfies “SR=1” or “SR=0”, in other words whether blur correction is inthe OFF state or in a state where the locking initialization operationis completed. When “SR≠1” and “SR≠0”, that is, when the current statusdoes not indicate that blur correction is in the OFF state and thelocking initialization operation has not been performed, the centeringdrive process illustrated in the flowchart of FIG. 11 is performed instep S406 and the lock ring 30 (see FIG. 2) is rotated to the lockedposition by driving the locking motor 44 in step S408. This situationoccurs when the blur correction switch 22 is switched from the ON stateto the OFF state, namely when the status is still maintained as “SR=2”.Namely, the correction lens 14 is not locked even though the blurcorrection is currently OFF, so that the correction lens 14 is locked inthe above process.

In step S410, the flag SR indicating the blur correction status is setto satisfy “SR=1” to indicate that the blur correction is OFF. In stepS412, power supply to the coils of the blur correction mechanism 13 (seeFIG. 6) is stopped to terminate the blur correction operation andthereby the current timer interruption process ends. When it isdetermined in step S404 that “SR=1” or “SR=0”, the timer interruptionprocess immediately ends.

On the other hand, when it is determined that the blur correction switch22 is in the ON state in step S402, it is determined whether or not theSR flag indicating the blur correction status satisfies “SR=2” in stepS414. When it is determined that “SR=2”, the blur correction is underwayso that the process proceeds to step S422 and terminates the timerinterruption process while continuing the blur correction drive process.When “SR≠2”, the blur correction is in the OFF state and the lock ring30 is in the locked state. In this case, a shift drive process(mentioned later) for the correction lens 14 is performed in step S416and the lock ring 30 is rotated to be in the unlocked state in stepS418. Then, after the SR flag of the blur correction status is set tosatisfy “SR=2” (blur correction ON) in step S420, the blur correctionprocess is started in step S422 and the timer interruption process isfinished in step S422.

When the RLS flag of the release status satisfies “RLS=1” in step S400,that is, when it is determined that a release operation is underway, itis determined whether or not the SR flag of the blur correction statussatisfies “SR=1 in step S424. When “SR=1”, that is, when the blurcorrection is in the OFF state, a later-mentioned current positionmaintenance drive process is performed in step S426 and the timerinterruption process is finished. On the other hand, when “SR≠1”, thatis, when it is determined that the blur correction status is in the ONstate, the blur correction drive process is continued in step S422 andthe timer interruption process is finished.

Next, the shift drive process of step S416 (see FIG. 10) will bedescribed with reference to FIGS. 2, 3, 6, and 12. Here, FIG. 12 is aflowchart of the shift drive process of step S416.

When the lock ring 30 is in the locked position (FIG. 3B), the fourprotrusions 28P arranged on the circular frame of the movable portion 28are in contact with the arc-shaped inner circumferential surface of thelock ring. However, since tolerance exists therebetween, the correctionlens 14 is movable in the locked range of motion 34 illustrated in FIG.3B. Here, the correction lens 14 drops in the direction of gravitationalforce when the blur correction is in the OFF state, so that theprotrusion 28P is in contact with the lock ring 30. Therefore, toeliminate frictional resistance due to contact of the protrusion 28P atthe time of unlocking, the protrusion 28P of the movable portion 28 isrequired to be apart from the lock ring 30 similarly to the lockinginitialization operation. However, when the centering drive process (seeFIG. 11) is performed as the locking initialization operation and thecorrection lens 14 is moved to the center of the range of motion 33, 34,the movement includes unnecessary motion and it takes more time torelease the lock.

In the present embodiment, the shift drive process for the correctionlens 14 (movable portion 28) is performed in step S416 instead of thecentering drive process of FIG. 11. In the shift drive process, first,the current position coordinates X, Y of the correction lens 14 areobtained based on the outputs of the Hall sensors 25X, 25Y in step S600.In step S602, the drive position coordinates X, Y of the correction lens14 are calculated with the following equations and set as the targetposition coordinates by the controller 39.drive position X=(current position X)×(1−α)drive position Y=(current position Y)×(1−β)

Here, α and β are simply required to be less than 1.0, but may be 0.5 orless. It is preferable that α and β are approximately in a range between0.05 and 0.2. That is, shift drive amounts ΔX, ΔY in the X-axisdirection and the Y-axis direction from the current positions X, Y areobtained as “ΔX=−(current position X)×α” and “ΔY=−(current positionY)×β, respectively. In the present embodiment, for example, both α and βare set to be 0.1. That is, in the shift drive process of the presentembodiment, the correction lens 14 is moved by 10% of the currentposition coordinates X, Y in −X and −Y directions along the X and Yaxes, with the center of the range of motion 33, 34 (i.e., optical axis)being the coordinate origin and the position of the correction lens 14being the lens center thereof. The above corresponds to the situationwhen the correction lens 14, which is shifted downward in the directionof gravitational force, is nudged toward the center by the order of 10%of the deviation distance.

In step S604, an automatic control calculation is performed withreference to the drive position coordinates X, Y calculated in stepS602. In step S606, the correction lens 14 is moved to the driveposition coordinates X, Y by driving the movable portion 28, and then,the shift drive process is finished.

Here, as illustrated in FIGS. 13A to 13D, the direction in which thecorrection lens 14 is displaced due to gravitational force varies inaccordance with the orientation of the camera. However, by using theequations to define the abovementioned drive position coordinates X, Y,the same simple expressions can be adopted for any case regardless ofthe direction of gravitational force. In FIG. 13, point P denotes thecenter position of the deviated correction lens 14 and corresponds tothe current position coordinates X, Y in each case.

Next, the current position maintenance drive process to be performed instep S426 of FIG. 10 will be described with reference to FIG. 14. Thecurrent position maintenance drive process is performed when the releaseoperation is started while the blur correction is in the OFF state. Whenthe blur correction is in the OFF state, the release operation isnormally performed while photography is conducted in a stable state,such as when the camera is mounted on a tripod, so that the correctionlens 14 is in the locked state. However, as described above, since thecorrection lens 14 is movable in the locked range of motion 34 even inthe locked state, the correction lens 14 can be moved during photographydue to vibration that may be caused by a release operation, and this maydeteriorate the resolution of the image.

Therefore, in the present embodiment, when a release operation isperformed while the blur correction is in the OFF state, photography iscarried out with the correction lens 14 being electromagneticallysuspended in the current position using the blur correction mechanismbefore any vibrations can be caused by mechanical operations, such as ashutter operation or mirror-up operation. Namely, the current positioncoordinates X, Y of the correction lens 14 are obtained based on thesignals of the Hall sensors 25X, 25Y in step S700 and the drive positioncoordinates X, Y are set to the current position coordinates X, Y by thecontroller 39 in step S702. An automatic control calculation isperformed based on the set drive position coordinates X, Y in step S704and the blur correction mechanism 13 is driven based thereon in stepS706. Namely, the correction lens 14 is electromagnetically locked inthe current position. In the present embodiment, the above process isperformed when the release switch 21 is turned on. However, the aboveprocess can also be performed when a photometric switch is turned onwith half depression of a release button.

Next, the blur correction drive process to be performed in step S422 ofFIG. 10 will be described with reference to FIGS. 1 and 6, and FIG. 15,which is a flowchart of the blur correction drive process.

In the blur correction drive process, first, angular velocity signalsabout the Y axis and the X axis are obtained from the angular velocitysensors (gyroscopes) 23X, 23Y in step S800. Rotational angles about theY axis and the X axis are calculated by the angle calculation units 36X,36Y in step S802. In step S804, the drive position coordinates X, Y arecalculated by the lens drive position calculation units 37X, 37Y(controller 39) based on the rotational angles calculated in step S802,lens focal length f, and the like. In step S806, the current positioncoordinates X, Y of the correction lens 14 are obtained by theX-direction drive controller 24X and the Y-direction drive controller24Y based on the signals from the Hall sensors 25X, 25Y. According tothe automatic control calculation in step S808, manipulation variablesare calculated by the automatic control calculation processors 40X, 40Yfrom the difference between the drive position coordinates X, Y and thecurrent position coordinates X, Y. Based on the manipulation variables,electric power is supplied to the X-direction coil 41X and theY-direction coil 41Y by the X-direction drive controller 24X and theY-direction drive controller 24Y to drive the blur correction mechanism13.

As described above, according to the structure of the first embodiment,since a movable portion is not supported to a fixed portion by anelastic support member such as an elastic body, blur correction can beperformed more efficiently. Meanwhile, according to such a structure,since the movable portion is not supported by an elastic support member,the weight of the movable portion including a correction lens issupported entirely by a locking mechanism (lock ring) via a contactportion (protrusions) when the blur correction control is in the OFFstate, and such contact will interfere with an unlocking operation.However, in the first embodiment, since a shift drive process is used toseparate the movable portion from the locking mechanism (lock ring) whena mechanical locking mechanism is being unlocked, unlocking can beeasily performed without excessive frictional force at the time ofunlocking. Further, in the present embodiment, since the correction lensis moved only slightly with the shift drive process, it is possible toreduce the amount of time until rotation of the locking mechanism (lockring) can be started. Accordingly, rapid unlocking can be performed.

Further, in the present embodiment, a small shift can be calculated witha simple expression, and a shift drive of the correction lens can becarried out by adopting only the structure of a conventional blurcorrection mechanism, regardless of a gravity sensor and the orientationof the camera body. Further, the present embodiment is effective when alarge amount of friction is caused by the weight of the movable portionapplied against the lock ring (locking member).

Further, according to the present embodiment, when a release operationis performed when blur correction is in the OFF state and the movableportion is mechanically locked, the movable portion iselectromagnetically locked in the position thereof using the blurcorrection mechanism. Accordingly, the correction lens can be preventedfrom making any movements within a range of motion due to the toleranceof the mechanical locking mechanism when vibration is caused by arelease operation, so that deterioration in the resolution of aphotographed image can be prevented. Further, since the electromagneticlocking is performed only during the release operation, it is possibleto suppress unnecessary power consumption.

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 16 to 18. The second embodiment is differentfrom the first embodiment in that the shift drive process in steps S416and S418 of FIG. 10 is replaced with a sinusoidal-drive unlockingprocess. The rest of the structure is the same as that of the firstembodiment. In the following, the same reference numbers have beenassigned to the same structures and the descriptions thereof will not berepeated.

FIG. 16, which corresponds to FIG. 10 of the first embodiment, is aflowchart of a timer interruption process with a 1 ms cycle time that isperformed by the lens CPU 18 in the second embodiment.

In the flowchart of FIG. 16, steps S900 to S914 and steps S920 to S926correspond to steps S400 to S414 and steps S420 to S426 in FIG. 10, andprocesses thereof are also similar thereto. Meanwhile, in step S916 ofthe second embodiment, the process of steps S416 and S418 of FIG. 10 isreplaced with the sinusoidal-drive unlocking process (gradual unlockingprocess). In the first embodiment, the correction lens 14, which hasbeen shifted downward in the direction of gravitational force, is movedtoward the center in the unlocking process by a small distance equal to10% of the deviation amount. In contrast, in the second embodiment,similarly to the centering drive of step S406, the center of thecorrection lens 14 is moved to the center (optical axis) of the range ofmotion 33, 34 in accordance with a later-mentioned sinusoidal-driveprocess.

A method of moving the correction lens 14 to the center position in thesinusoidal-drive unlocking process (gradual unlocking process) of thesecond embodiment will be described with reference to FIG. 17.

FIG. 17 is a graph indicating positional changes of the correction lens14 (movable portion 28) with the centering drive processes of steps S406and S906 and the timing of switching between the locked position and theunlocked position of the lock ring 30. Curved line L1 indicates atemporal change of the position of the correction lens 14 (movableportion 28) with the centering drive process. Curved line L2 indicates atemporal change of the position of the correction lens 14 (movableportion 28) with the sinusoidal-drive unlocking process. Curved line R1indicates the movement of the lock ring 30 from the locked position tothe unlocked position when the centering drive process is performed.Curved line R2 indicates the movement of the lock ring 30 from thelocked position to the unlocked position when the sinusoidal-driveunlocking process is performed.

In the centering drive process, the drive position coordinates X, Ydesignate the target position for the movement control of the correctionlens 14 and are set as the origin (0, 0), which is the center position(optical axis) of the range of motion. The correction lens 14 is thenmoved to the center position with an automatic control calculation suchas PID. As illustrated by the curved line L1, fluctuation occurs as thecorrection lens 14 converges toward the center position. Here, theunlocking operation is performed after the correction lens 14 is movedto the center position and time T1 is required for unlocking.

In contrast, in the sinusoidal-drive unlocking process, the driveposition coordinates X, Y designating the target values are graduallyapproximated to the center position. Accordingly, the correction lens 14is also moved toward the center position using the drive positioncoordinates X, Y. In the present embodiment, the correction lens 14 iscontrolled to be moved toward the center position along crest-to-troughor trough-to-crest (peak-to-peak) intervals that are one half cycle of asine wave. Here, the unlocking operation of the lock ring 30 is started,for example, at a phase in a range between 0° and 90° (before arrivingat the halfway point of the distance from the initial position to thecenter) and the lock ring 30 is moved to the unlocked position beforemovement of the correction lens 14 to the center position is completed.That is, time T2 required for unlocking is equivalent to the timerequired for moving the correction lens 14 to the center position.Incidentally, the time required for moving the correction lens 14 to thecenter position is approximately the same in both the centering driveprocess and the sinusoidal-drive unlocking process.

In the centering drive process, since the correction lens 14 vibratesbefore arriving at the center position, there is a possibility that theprotrusion 28P of the movable portion 28 makes contact with the lockring 30. Accordingly, the unlocking operation is performed after thecentering drive process is completed. In contrast, in thesinusoidal-drive unlocking process (gradual drive unlocking process),since the correction lens 14 gradually approaches the center position,the protrusions 28P of the movable portion 28 do not make contact withthe lock ring 30 provided that the correction lens 14 is approximated tothe center at a predetermined distance therefrom. Accordingly, it ispossible to start the unlocking operation during movement of thecorrection lens 14, so that time required for unlocking can beshortened.

FIG. 18 is a flowchart of the sinusoidal-drive unlocking process (stepS916 in FIG. 16) of the present embodiment. In the sinusoidal-driveunlocking process, first, a phase θ is initially set to 0 in step S1000.In step S1002, the current position coordinates X, Y of the correctionlens 14 are obtained using the Hall sensors 25X, 25Y. In step S1004,values of the drive position coordinates X, Y are obtained based on thecurrent position coordinates X, Y (initial position) and the phase θ.That is, the values of the drive position coordinates X, Y arecalculated with the following equations.drive position X=(current position X)×(cos θ+1)/2drive position Y=(current position Y)×(cos θ+1)/2

In step S1006, an automatic control calculation is performed based onthe current drive position coordinates X, Y. In step S1008, thecorrection lens 14 is moved to the calculated drive position withcoordinates X, Y. In step S1010, the value of the phase θ is updated toθ+Δθ. Here, θ denotes a phase angle having the unlocking time T2 of ahalf cycle and an increment Δθ may be 1. However, the value of Δθ may belarger than 1 or smaller than 1 as long as it is a positive value.

Next, in step S1012, it is determined whether or not the value of θarrives at a predetermined value such as 90°. The predetermined value(e.g., 90°) specifies the timing when the unlocking operation of thelock ring 30 is started. When “θ=the predetermined value (e.g., 90°)” issatisfied, the unlocking operation is started in step S1016. In othercases, in step S1014, it is determined whether or not “θ>180°” issatisfied, that is, whether or not the movement is completed.

When “θ>180°” is not satisfied, that is, when movement to the centerposition is not completed, the process returns to step S1004 so that thenew drive position coordinates X, Y are calculated based on the value ofθ updated in step S1010 and the initial position coordinates X, Y, andthen, the similar processes are repeated. On the other hand, when it isdetermined that “θ>180°” is satisfied in step S1014, the process isfinished.

In the present embodiment, the drive positions X, Y follow a sine wavepath. However, it is only required that the distance from the initialposition (current position) to the center position varies against timewith a monotonically decreasing function, that is, movement is performedso that the distance to the center is always smaller than the previousdistance thereto. It is preferable to arrive at the center positionparticularly in the latter half, with the use of gradual acceleration.Further, gradual acceleration is preferable in the first half. Forexample, in the latter half the movement speed decelerates with time.

As described above, according to the second embodiment, it is possibleto obtain effects similar to those of the first embodiment. In thesecond embodiment, the unlocking time is slightly longer than that ofthe first embodiment. However, since the correction lens is smoothlymoved to the center position, it is possible to prevent uncomfortableimage blur occurring in a through-the-lens image during unlocking.

In the above description, the present embodiment is applied to alens-shift type of blur correction mechanism as an example. However, thepresent invention can be applied to a blur correction mechanism thatuses an image sensor shift. Further, the present invention can beapplied to a mirror-less camera, a camera with a non-replaceable lens,and a camera having only a finder without an image display monitor. Forexample, in the structure with only a finder, the fact that aphotometric switch has been turned on is the only information suppliedto the lens CPU in step S106, and the processes of steps S108 to S116are eliminated. Further, in the present embodiment, descriptions areprovided as exemplifying a digital camera. However, the presentinvention can be applied to a silver film camera as well.

In the present embodiment, the lock ring is adopted as the lockingmember. However, the present invention is not restricted to a lockingmechanism of the type discussed in the present embodiment. For example,a locking mechanism including a pin member that is inserted into a holeformed in a movable portion may also be adopted.

Although the embodiment of the present invention has been describedherein with reference to the accompanying drawings, obviously manymodifications and changes may be made by those skilled in this artwithout departing from the scope of the invention.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2012-203594 (filed on Sep. 14, 2012), which isexpressly incorporated herein, by reference, in its entirety.

The invention claimed is:
 1. A blur correction apparatus, comprising: ablur correction mechanism that compensates for camera shake by driving amovable portion provided with one of a correction lens and an imagingdevice; a locking member which restricts movement of the movable portionwithin a locked range of motion; a shift drive processor which moves themovable portion a predetermined distance toward a center of the lockedrange of motion when locking by the locking member is released, thepredetermined distance being shorter than the distance from the movableportion to the center; and an unlocking driver which moves the lockingmember to an unlocked position after moving the movable portion thepredetermined distance away from the locking member; wherein the movableportion is suspended in a current position by the blur correctionmechanism when a release operation is performed in a state in which themovable portion is locked by the locking member.
 2. The blur correctionapparatus according to claim 1, wherein the predetermined distance isequal to or less than 50% of the distance from the movable portion tothe center.
 3. The blur correction apparatus according to claim 1,wherein the shift drive processor is activated when blur correctionstarts.
 4. The blur correction apparatus according to claims 1, whereinthe movable portion includes a circular frame portion; the lockingmember is a lock ring which surrounds the periphery of the circularframe portion; a plurality of protrusions are arranged on an outercircumference of the circular frame portion; a plurality of recessescorresponding to the plurality of protrusions are arranged on a circularinner circumference of the lock ring; the lock ring is movable between alocked position and the unlocked position; in the locked position,movement of the movable portion is restricted by contact between theprotrusions and the circular inner circumference; and in the unlockedposition, the protrusions are aligned with the recesses so that themovable portion is made movable for blur correction.
 5. A lens barrel,comprising: a blur correction mechanism which compensates for camerashake by driving a movable portion provided with a correction lens; alocking member which restricts movement of the movable portion within alocked range of motion; a shift drive processor which moves the movableportion a predetermined distance toward a center of the locked range ofmotion when locking with the locking member is released, thepredetermined distance being less than the distance from the movableportion to the center; and an unlocking driver which moves the lockingmember to an unlocked position after moving the movable portion by thepredetermined distance away from the locking member; wherein the movableportion is suspended in a current position by the blur correctionmechanism when a release operation is performed in a state in which themovable portion is locked by the locking member.
 6. The blur correctionapparatus according to claim 1, wherein one of a centering driveprocess, a shift drive process, and a sinusoidal drive unlocking processis performed when the blur correction is in an OFF state.
 7. The lensbarrel according to claim 5, wherein one of a centering drive process, ashift drive process, and a sinusoidal drive unlocking process isperformed when the blur correction is in an OFF state.